Need a physics genius!

A 591 kg car stopped at an intersection is rear-ended by a 1850 kg truck moving with a speed of 16.5 m/s. If the car was in neutral and its brakes were off, so that the collision is approximately elastic, find the final speed of both vehicles after the collision.

Final (car) A)
Final (truck) B)

A useful trick to know here is that elastic collisions always reverse the relative velocity before the collision. i.e. in this case, the car will be going exactly 16.5 m/s faster than the truck. (Initially the truck was 16.5 m/s aster than the car).

i.e. the car's final speed is vcf = vtf + 16.5

Initial momentum = final momentum = mt * vti = 1850 * 16.5 kg.m/s = 30525 kg.m/s

so mc*vcf + mt*vtf = 30525

591*(vtf + 16.5) + 1850*vtf = 30525

vtf = (30525 - (591*16.5) ) / (1850+591) = 8.50 m/s <= ANS B)

vcf = 8.50 + 16.5 m/s = 25.0 m/s <= ANS A)